1. Field of the Invention
This invention pertains to processing insulated electrical conductors, and more particularly to apparatus for accurately positioning and displaying information representing the positions of wire stripping blades.
2. Description of the Prior Art
Recent trends in the automotive and electronics industries have been to use ever smaller gauge insulated electrical and thinner wall insulations. In automotive applications, that trend is the result of the increased usage of on-board electronics, the increased usage of longer wire lengths to reduce the number of connectors and splices, and the limited space available for wire passages. Presently, automobiles manufactured in the United States contain an average of approximately 1900 feet of insulated wire, of which 70% is classified as thin wall. Thin wall wire is defined as having a minimum insulation wall thickness of approximately 0.11 inches. It is estimated that by 1992 an average of approximately 2400 feet of wire will be used in every automobile, 90% of which being thin wall. In deed, experimental ultra thin wall wire is now being considered for future applications.
The trend to smaller insulated electrical conductors has caused considerable problems with precisely and reliably stripping the very thin insulations. Suitable blades for stripping very thin insulation have been developed, and they are commercially available. For example. U.S. Pat. No. 4,577,405 describes stripping blades that work very well with thin wall insulation. In addition, methods are known by which the optimum stripping blade hole size for a particular conductor/insulation combination can be accurately predetermined. Other methods have been developed for selecting the closest available "best-fit" blade hole size. On the other hand, prior wire processing machinery itself is generally not capable of precisely and reliably closing stripping blades to a desired specific cutting hole size. For example, while new techniques may enable a calculation to be made that 0.051 inches is the optimum diameter of the stripping blade cutting hole for a twenty gauge conductor with thin wall insulation, it is virtually impossible for prior machinery to set the blade hole to that size.
To meet the demand for a precision and reliable machine for cutting and stripping insulated electrical conductors, the wire processing machine described in co-pending U.S. Pat. application Ser. No. 235,213, now U.S. Pat. No. 4,961,357, dated Oct. 9, 1990 was developed. That machine has a cutterhead that is guided in a common plate to open and close over the insulated electrical conductor being processed. The two tool holders of the cutterhead are adjustable independent of each other along two cutterhead slides. The machine of U.S. Pat. No. 4,961,357 is exceptionally rigid, and it is constructed to maintain precision performance on a long term basis.
It has been found desirable that wire processing machines include a system that provides information to the machine operator of the actual blade hole size at a particular blade setting and with particular blades clamped in the cutterhead. Prior equipment does not possess such capabilities. As a result, at present the blades are adjusted open or closed based on a visual inspection of a test wire strip. If the test strip results in a cut, nicked or scraped conductor, the blade hole is adjusted open. If the insulation is not properly pulled off the test strip, the blade hole is closed. Such trial-by-error methods cannot meet present demands for efficiently and precisely processing thin wall/small gauge conductors on a production basis.